A gasket composition having a viscosity of 4,000-100,000 centipoises at 25° C., which comprises (A) an urethane acrylate oligomer having a weight average molecular weight Mw of 7,000-40,000, (B) monoacrylate of terminally substituted polyether or polyether-polyester, and (C) a photo-polymerization initiator, is disclose (WO96/10594), and it is states that gaskets for precision appliances can be made from the foregoing gasket composition simply by coating the composition by an automatic coating robot, followed by irradiation with ultraviolet rays with less generation of gas components, but in view of such a viscosity of the composition it would be hard to simply process gasket shapes requiring a high sealability. That is, due to such a low liquid viscosity, it would be impossible to obtain the necessary gasket cross-sectional height for fully attaining the required sealing performance.
To overcome the problem, processes for efficiently producing HDD gaskets having a chevron-shaped cross-section with a high sealability by an automatic coating robot from a photo-curable liquid material with an improved thixotropical property by addition of an inorganic filler have been proposed (JP-A-2001-225392 and JP-A-2003-105320). However, these processes would be inadequate for the production of HDD gaskets now requiring a high humidity barrier function due to the presence of the inorganic filler of highly hydrophilic property.